The invention is based on a valve control apparatus having a magnet valve for internal combustion engines as defined hereinafter.
In a previous valve control apparatus, for controlling the closing and opening time of a motor valve, actuated by a valve control cam of a camshaft via an axially displaceable valve shaft (German Patent Application No. 38 15 668.7, now U.S. Pat. No. 4,889,084), the liquid reservoir is integrated with the magnet valve, and the valve element serves as a reservoir piston that divides a reservoir chamber from a magnet chamber; the communication between the valve inlet and the reservoir chamber is controlled via one end edge of the reservoir piston in cooperation with the valve seat. The magnet acts counter to the reservoir deflection direction, because in this special exemplary embodiment the magnet valve is intended to be open when without current or in other words to be blocked only when voltage runs through it. This is intended to assure that the motor cannot race should the plug fall off the magnet valve. Achieving the embodiment of the invention as set forth above, in which on the one hand the fluid reservoir is integrated with the magnet valve and on the other the magnet valve is intended to be open when without current, entails considerable expense, in particular for construction, above all because at least two springs must engage the reservoir piston serving as the valve element. If the spring acting in the valve opening direction is to be accommodated within the magnet valve, the region of the reservoir chamber located underneath the valve seat must have a minimum structural size. Since this region is always filled with hydraulic fluid, however, the result is not an enlargement in the reservoir chamber but rather a disadvantageous enlargement of the total structural size of the magnet valve.